In last week’s tip I said that cardio training doesn’t help with weight loss, or at least not in the way that many people perceive. This week I’m going to dig a little deeper into that idea. And next week I’ll finish up with an overview of a more efficient cardio strategy for a variety of outcomes, from physical performance to weight management.
So you might be thinking, “How does cardio not help with weight loss? It burns calories, right?”
Yes, movement of any kind does require energy. So adding some cardio training to your day could lead to an energy deficit, assuming that you consume less than you expend. And that would eventually produce some weight loss.
But there are a few problems with this transactional way of viewing cardio training’s effect on weight management:
Imprecision
We run into a few issues of precision on the consumption side of the consume/expend equation including miscalculated serving sizes, differences between reported calories (based on nutrition labels) and actual calories (based on numerous factors), and foods’ levels of processing, among other factors.
Just as much, if not more, variability also occurs on the expenditure side of the equation. Some examples include differences in reported energy expenditure (via generic equations built into heart rate monitors or pace from a treadmill, bike, etc.) and actual energy expenditure (due to training background and body composition), fidgeting and other daily activities, and variations due to stress or lack of sleep.
And it doesn’t take a math wiz to recognize that imprecision on both sides of an equation rarely leads to the correct answer.
Inefficiency
To understand this and the next point, a high-level understanding of the body’s three energy-producing systems is helpful. (I’ll keep this brief and hopefully easily understandable. For the detail-oriented, science folks, I apologize for the overgeneralizations.)
For each system, let’s consider three factors: fuel source, production rate, and capacity (or duration over which the system provides energy).
- ATP-CP / Alactic system
- Fuel source: creatine phosphate
- Production rate: fast
- Capacity/duration: under 10-15 seconds of extremely intense activity (e.g. max weight deadlift for one rep, 100m sprint)
- Glycolytic system
- Fuel source: glycogen (the muscle’s storage form of glucose… i.e. a carbohydrate)
- Production rate: moderate
- Capacity/duration: a few minutes of moderately intense activity (e.g. 15 reps of any exercise with a weight that you couldn’t do for a single rep more, 400-800m run). Note: This system produces lactic acid and hydrogen ions as byproducts and, subsequently, the “burning” sensation that muscles can experience during activity
- Aerobic system
- Fuel source: fat
- Production rate: slow
- Capacity/duration: hours to days of less intense activity (e.g. 10 reps of any exercise with a weight that you could lift for 30+ reps, marathon, triathlon, long hike or ruck, digestion)
“Traditional” cardio training—that is, spending 30-60 minutes or more at a relaxed to moderate pace on a bike, treadmill, hike, or something similar—is performed at a relatively low intensity (see zones 2 and 3 in last week’s tip). During this style of training, the body gets most of its energy from the aerobic system.
That causes a problem for our weight management case study precisely because the system is highly efficient. That is, it produces energy relatively slowly, but the energy it produces comes from a small quantity of fuel. (i.e. Fat is very “energy dense”.)
In other words, we can spend an hour or two on the treadmill (or similar activity), and actually burn only a few hundred calories. And the next time we eat, those calories go right back into the system (especially if we miscalculate a serving size).
If weight loss has been your goal and you’ve spent near-countless hours doing low-intensity cardio training with minimal results, this is at least part of the reason.
Unsustainability
At this point, you might be thinking something along the lines of, “That makes sense, but it’s also why I’ve switched to HIIT (high-intensity interval training) for my cardio… because it burns more calories in the same amount of time.”
If that’s the case, I’ll not only agree with you but also add that you’re likely expending more energy after training too—up to 20% more than normal over the subsequent 24-36 hours.
But here’s the rub: this style of training potentially makes a lot of use of both the alactic and aerobic systems at various times, but it also very often makes use of the glycolytic system.
Periodically or as part of a short-term peaking protocol (in preparation for a sporting event, photo shoot, vacation, etc.), that can be quite beneficial. But if it progresses into a frequent, long-term practice, you’re significantly more likely to get burned out, injured, and/or experience long plateaus or regressions of training adaptations. (In other words, you’re likely to get weaker, slower, and possibly experience an increase in body fat percentage.)
Putting it into practice
So the next question becomes: How might we best use cardio training as part of a plan to improve our performance or manage our weight?
I’ll suggest that we adopt a structural as opposed to transactional view of cardio’s effects and it’s usefulness in achieving certain goals. Tune in next week for details on that and how it relates to… M&Ms!?!
For now, continue with last week’s suggestion of getting in a brief walk after dinner (if you’re currently somewhat sedentary) or simply sticking with your current training (if you’re generally more active). Even though traditional cardio training may not be the most efficient approach for managing weight, its general health benefits can’t be overstated.